1. Field of the Invention
The invention relates to a computer architecture particularly adapted for high bandwidth, high concurrency and multitasking operations.
2. Description of the Related Art
Computer systems are being developed with more powerful and advanced features with each passing moment. Many new advanced bus structures such as the PCI, or Peripheral Component Interconnect, bus have been developed to allow greater performance of the computer system. Additionally, new communications buses such as Universal Serial Bus and I.E.E.E. 1394 (Institute of Electrical and Electronic Engineers) a.k.a. Firewire, have been developed as the modem personal computer is becoming a much more connected and multimedia oriented system.
However, certain functions such as graphics and video are being required to manipulate ever increasing amounts of data. High resolution screens, such as 1280.times.1024, and true-color modes, such as 16 million colors, require large frame buffers to store data representing screen pixels. Conventionally, the computer system maintains two frame buffers: one in main memory which the processor writes to; and one in the display subsystem for the temporary storage of data as it is moved from main memory to the screen. This duplication and the frame buffer size causes the memory requirements to be not insignificant.
To address some of these concerns, and to lower overall system cost, it has been proposed that a unified memory architecture (UMA) be developed in which the display frame buffer not be separate, but be integral with system memory. Thus, the step of moving the data from system memory to graphics memory is eliminated at the expense of more memory accesses. Although this solution succeeds in lower costs, it is not preferable since it decreases overall system performance.
A further complication develops if 3-dimensional (3D) or virtual reality features are to be performed because data must first be heavily manipulated. Thus, in addition to the memory requirements discussed above, further processing and data movement is required. Thus, system memory soon becomes a bottleneck for the computer system. Full screen video requires this data to be supplied to the display at a rate of at least 30 frames per second. These specifications singly cause most of the bandwidth of the PCI bus to be exhausted.